Arc-extinguishing cut-out.



PATENTED APR. 1'7, 1906.

E. M. HEWLETT. ARC EXTINGUISHING GUT-OUT.

APPLICATION FILED AUG.8, 1903.

FICH.

MT E5655: 4/2

No. 818,376. PATENTBD APR.1'7, 19%.

E. M. HEWLETT.

ARC BXTINGUISHING CUT-OUT. APPLICATION FILED AUG. 8. 1903.

2 SHEETS-SHEET 2 IN MENTOR} Edv/ar'd MHev/lett. M (2 b M UNITED sTATEs PATENT OFFICE.

EDWARD M. HEWLETT, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEI'V YORK.

ARC-EXTINGUISHING CUT-OUT.

Specification of Letters Patent.

Patented April 17, 1906.

Application filed August s, 1903. Serial No. 168,774.

' 1s a specification.

The object of my invention is to provide a current-interrupting device of the type in which a magnetic field is employed to deyelop an expulsive action on the arc-gases to quic ly sever the arc-stream and. open the current. Devices of this kind have been heretofore employed in thermal cut-outs or fuses and switches or circuit-breakers, a socalled blowout coil being utilized to develop the magneticfield which determines the expulsive action on the arc-gases. The introduction of the coil for this purpose in volves a considerable portion of the expense of the current-interrupting device and in addition, particularly in the case of switches or circuit-breakers of large current-carrying volume, creates a drop of potential across the main contacts which are opened a moment before the shunt-contacts, and therefore causes damage to such contacts by small arcs which burn them.

In my present invention I dispense with the blow-out coil and establish the magnetic field by means of the partial turn formed by the terminals and arc-stream, the terminals bein mounted in the chute, at the sides of whic are iron plates, which form a good magnetic circuit. This construction results in the great advantage of minimizing the drop of potential at the main contacts which are completed within the chute, thereby pre venting their burning, besides conducing to ward greater simplicity of construction, which greatly cheapens the cost. In order to give a definite path of expulsion to the arc, the iron plates at the sides of the chute are connected at a point outward from the contacts in the direction of expulsion by an iron path, which forms a short circuit across the iron plates at that point for the lines of force, thereby creating in the direction of expulsion a field of weaker magnetic density than exists between the plates at or below the ter minals, thus giving a definite direction to the expulsive blast and preventing the are. from diffusing or blowing back on the terminals or any other portion of the operating mechanism. This arrangement insures a greater density of field behind the arc, which thereby causes a progressive expulsive effect until the arc is ruptured. The arrangement is particularly effective with currents of large volume. I also provide at the outer part of the movement of the movable contact in the case of a switch or circuit-breaker a fixed terminal of approximately the same potential,

as the movable terminal of the switch, which in case the arc hangs until the limit of move ment of the movable member is completed takes the arc from the movable contact and prevents serious damage to the latter.

My invention therefore comprises means for rupturing a circuit comprising a chute or inclosure so arranged that a magnetic field of weaker density in the direction of expulsion or the direction away from the terminals is provided.

It comprises also a chute having sides of iron, that portion of the magnetic circuit beyond the terminals being of lower reluctance than the portion lying near the terminals.

It comprises also means for short-circuiting the movable contact at a definite point of its travel to prevent excessive burning.

It comprises also other features of novelty, which will be hereinafter pointed out and will be definitely indicated in the claims.

In the accompanying drawings, which illustrate one embodiment of my invention, is shown a switch or circuit-breaker of a special type designed for the interruption of currents of large volume and considerable potential, although, as hereinbefore pointed out, the invention is of general application to all kinds of current-interrupting devices.

Referring to the drawings, Figure 1 is a side elevation of such a switch or circuitbreaker. Fig. 2 is a detail view of the blow out chute, and Fig. 3 is a detail of the tripping device.

' The particular type of switch shown in the drawings has been fully described in my former patent, No. 677,353, dated July 2, 1901, to which references may be made. The essential features only will therefore be described.

1 represents an insulating-support of slate or o her fireproof material, and 2 2 circuitterminals of large current-carrying capacity rigidly mounted and provided with means on the rear for connecting the bus-bars or other current-carrying conductors. Between these terminals is a low standard 3, in which is journaled a frame 4, composed of two arms extending outwardly from the board, in which is journaled a handle 5. Rigid with the handle is a latch 6, connected by links 7 to a frame 8, carrying a bridging contact of laminae of phosphor-bronze 9, which is adapted to bridge the circuit-terminals 2 2 The latch 6 and links 7 form a toggle, which may be latched in the frame 4, so as to hold the circuit closed. This latch may be tripped by a bundle of iron plates 11, partly surrounding the terminal 2 An arc-shaped link 12 is pivoted to a fixed part of the frame work at the lower end and at the upper end pivotally connected with the link on which the bridging contact is suspended, the effect being that when the toggle is sprung the circuit-breaker under the joint influence of the elasticity of the bridging contact and gravity falls open, the arched link 12 arresting the parts by engaging in, the frame 4. These parts are merely typical, as the essential feature of my invention resides not in the mechanism of the switch, but in the arc-rupturing means and other features above referred to. In shunt to the main contact effected by the copper brush is an auxiliary contact inclosed by the same chute 13. This is preferably formed of two iron plates 13 and 13 formed of soft iron and connected above the terminal by an iron yoke or connecting-piece 14. The location of this piece is extremely important, as it determines the direction of blast of the arc, as will be hereinafter set forth. The chute between the iron plates is lined on the inside with fiber plates 15 15 and is open at the top and bottom. The

shunt-contacts 16 16 are preferably formed of carbon by reason of the uniformity of con tact under repeated 0 eration afiorded by this material. One car on piece may be embedded in or secured to the circuit-terminal, and the other is carried by the flexible copper-conductor 17, movable with the bridging contact or brush, but having a fixed connection with the other terminal of the circuit.

Within the arc-chute near the outer part is the metal contact 19, connected by the conductor 20 with terminal 2*. This contact may be mounted on a fiber partition 21 across the end of the chute. 18 represents a cross-piece of fiber. The contact 19 being at practically the same potential as the movable contact prevents the arc-gases from being blown by the magnetic field upon the mechanism of the switch. With this construction on opening the circuit the bridging contact first opens the shunt-contact by reason 'of the elasticity of the metal connection which carries it still remaining closed, '65 and the absence of a blow out in the circuit reduces the impedance of the shunt-path at the moment of rupture to such a low value that there is not sufficient difference of potential to cause any arcing at the bridging contact, thereby effectually preventing any burning or pitting of the latter. When the movable element has progressed sufficiently far to open the shunt-contact, the arc between the two shunt-contact members develops a magnetic field which follows the iron sides of the chute. This field is of the greatest density at the lower part of the chute, the iron yoke 14 forming a short circuit for the magnetic lines of force at the up- 0 per part, thereby establishing an area of low density of flux in the upper part. Thus there will be a differential effect upon the arcstream, the dense field below pushing it toward the upper end of the chute until it is l stretched to a point where it ruptures and opens the circuit.

With magnetic blow-outs as commonly constructed it has been found necessary to employ a number of supplementary breaks in addition to the main contacts opening progressively in order to guard against difierences of potential which would result in burning the contacts, ultimately rendering the cut-out device unfit for service. This result inheres from the combined inductance and resistance of the blow-out magnet commonly em loyed to develop the expulsive magnetic eld, the drop of potential across this impedance being sufficient to cause an arc to spring from the main terminals. With my present organization, however, it will be seen that there is no blow-out coil, and as both the shunt and main contact are located in the same magnetic field the drop of potential is equalized, the difference being due solely to possible difference of conductivity. The iron yoke 14 is of extreme importance 1n giving a definite direction to the arc-vapor. In forming a bridge or path of low reluctance above the terminal almost no lines of force will pass from iron plate to iron plate across this portion of the chute, whereas in the lower part of the chute all of the flux passes across the airgap. The net result of this is that the arc-stream is re elled from the neighborhood of the termina and driven with certainty toward the top of the chute, and the area of dense field follows the are as it bows upward.

The fixed contact 19 when the switch is fully open engages the movable shunt-contact. The are always bows or arches more or less and sometimes to such an extent as to turn almost horizontal near the shuntcon r2 5 tact, and this would cause a reverse direction of expulsion at that point. The fixed contact and fiber partition 21 prevent this, the

former taking the arc from the shunt-contact and the latter preventing the lateral spreading of the are.

What I claim as new, and desire to secure by Letters Patent of the United States, is-

1. An electric switch or circuit breaker having an arc-expelling chute inclosing both a main and shunt contact, both main and shunt contacts having substantially the same impedance.

2. An electric switch or circuit breaker having main and shunt contacts of substantially the same reactance, and a blow-out magnet in inductive relation to bothcontacts.

3. An arc-extinguishing cut-out having the points of circuit rupture completely inclosed by a ma netic circuit, the magnetizingcurrent for win traversing the contacts and the arc.

4. An arc-extinguishing cut-out having its points of circuit rupture between iron polepieces extending across the gap at the sides thereof, the magnetizing-current for which is furnished by current traversing the contacts and are.

5. An electric switch or circuit breaker having a main and shunt contact inclosed in an arc-rupturing chute between iron polepieces, the two pairs of contacts being of the same reactance.

6. An electric switch or circuit -breaker having main and shunt contacts, a chute in which they move on opening the circuit, and

ch is furnished by current.

a metal contact electrically connected with the shunt to take the arc after a definite range of movement of the movable contact and thereby prevent deflection of the arcgases.

7. An electric switch or circuit-breaker having mainand shunt contacts, a chute in which they move, an insulating-partition across the end of the chute, and an arcingcontact near the partition electrically connected with one circuit-terminal.

8. The combination with a current interrupter or cut-out, of means for localizing. the magnetic flux on the side nearest the terminals, said means comprising plates of magnetic material at the sides of'a chute inclosing the terminals, and a magnetic connection between the plates.

9. A current interrupter or cut-out havin an arc-chute at the side of the terminals and walls of magnetic material connected by a short-circuiting connection on the side away from the terminals.

10. A current interrupter or cut-out having a magnetic circuit of good ermeability inclosing both terminals, the fiel in the direction of expulsion being of less reluctance than the other parts.

In witness whereof I have hereunto set my hand this 7th day of Au ust, 1903.

EDWAR Witnesses:

EDWARD WILLIAMS, Jr.. M. EDITH SILLIMAN.

M. HEWLETTv 

